Method for deeply discharging waste lithium ion battery

Abstract

The invention discloses a method for deeply discharging a waste lithium ion battery, and belongs to the technical field of waste lithium ion battery recovery. The invention provides an electrolyte for deep discharge of a waste lithium ion battery. Anions in the electrolyte are one or a combination of several of hydroxyl ions, sulfate ions, carbonate ions, nitrate ions, phosphate ions or perchlorate ions; cations in the electrolyte are at least one of metal ions or metal complex ions which can be electrodeposited in an aqueous solution. According to the method, a strategy of replacing hydrogen evolution with metal deposition is adopted, the electrolyte for chemical discharge of the waste lithium ion battery is optimized, hydrogen easy to burn and explode is avoided, the discharge efficiency is high, the process is safe and reliable, and the method is suitable for industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste lithium-ion battery recycling, and specifically relates to safely and conveniently completing the deep discharge of waste lithium-ion batteries through chemical methods, which is convenient for subsequent material crushing and separation and valuable metal recovery. No waste liquid or waste gas is discharged during the process, which is environmentally friendly and safe. Background Art

[0002] With the widespread use of lithium-ion batteries, waste ternary lithium-ion batteries contain high-value metals such as lithium, cobalt, manganese, and nickel, and waste lithium iron phosphate also contains lithium, iron, etc., which can be recycled and reused. The recycling of waste lithium-ion batteries mainly includes two processes: pretreatment and valuable metal recovery. Pretreatment includes the discharge and disassembly of the battery, the crushing and screening of the battery core, etc. After pretreatment, the positive and negative electrode material powders are obtained, and then the valuable metals are recovered by pyrometallurgical or hydrometallurgical processes. Due to the high residual voltage, waste lithium-ion batteries must be deeply discharged before recycling to ensure the safety of subsequent processes.

[0003] At present, there are two main ways to safely discharge waste lithium-ion batteries. One way is physical discharge, which is to connect the positive and negative electrodes of the battery to the discharge circuit and consume the residual power in the battery through resistance. This is usually suitable for laboratories. In the industrial recycling process, physical discharge is labor-intensive and time-consuming for a large number of waste lithium-ion batteries of different specifications, and is not feasible. Therefore, the commonly used method is chemical discharge, which is to immerse the waste lithium-ion battery in an electrolyte solution, use the residual voltage of the battery to trigger the electrochemical reaction between the positive and negative electrodes, and consume the residual power in the battery through the electrolysis process.

[0004] At present, chemical discharge usually uses low-cost sodium chloride solution as electrolyte. The chloride ions in the solution are oxidized at the positive electrode of the battery to produce chlorine gas, and the water molecules are reduced at the negative electrode to produce hydrogen gas. The explosion range of hydrogen in the air is between 4.0% and 75.6%, and the chlorine gas formed simultaneously is also highly oxidizing, polluting the environment. Therefore, the usual discharge process has a great risk of combustion and explosion. In addition, sodium chloride solution will also corrode metal parts such as battery casings and tabs, and produce sewage with harmful floating objects. For this reason, it is urgent to develop a convenient and safe deep discharge method for waste lithium-ion batteries, so that the entire discharge process does not produce waste gas and waste liquid, the cost is low, and the waste lithium-ion battery recycling process is green and safe. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, in order to solve the problem that the existing electrolyte such as sodium chloride generates hydrogen gas that is easy to ignite and explode, chlorine gas and waste water that pollute the environment during the chemical discharge of waste lithium-ion batteries, the purpose of the present invention is to design and provide a method for deep discharge of waste lithium-ion batteries. The present invention adopts the strategy of metal deposition instead of hydrogen evolution, designs an electrolyte for chemical discharge of waste lithium-ion batteries, avoids the generation of hydrogen gas that is easy to ignite and explode, and only generates environmentally friendly oxygen, with high discharge efficiency, safe and reliable process, and is suitable for industrial application.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides an electrolyte for deep discharge of waste lithium-ion batteries, wherein the anions in the electrolyte are one or a combination of hydroxide, sulfate, carbonate, nitrate, phosphate, and perchlorate ions;

[0008] The cations in the electrolyte are one or a combination of metal ions that can be electrodeposited in an aqueous solution.

[0009] The electrolyte for deep discharge of waste lithium-ion batteries, wherein the metal ions that can be electrodeposited in the aqueous solution are one or a combination of chromium ions, manganese ions, iron ions, cobalt ions, nickel ions, copper ions, zinc ions, gallium ions, tellurium ions, ruthenium ions, rhodium ions, palladium ions, silver ions, cadmium ions, indium ions, tin ions, antimony ions, rhenium ions, osmium ions, iridium ions, platinum ions, gold ions, mercury ions, thallium ions, lead ions, bismuth ions or polonium ions.

[0010] In a second aspect, the present invention provides a method for deep discharging a waste lithium-ion battery, comprising the following steps:

[0011] The waste lithium-ion battery is immersed in any of the electrolytes described above, so that the deposition potential of the metal ions in the electrolyte is higher than the hydrogen evolution potential to prevent hydrogen evolution, and a discharge chemical reaction is performed to a voltage of 1V or less to complete the deep discharge of the waste lithium-ion battery, and the electrolyte and the battery are collected separately.

[0012] In the method, when the deposition potential of the metal ions in the electrolyte is not higher than the hydrogen evolution potential, a metal ion complex is formed to make the hydrogen evolution potential lower than the metal deposition potential.

[0013] According to the method, the collected electrolyte can be recycled after adjusting the composition.

[0014] According to the method, the collected electrolyte can be recycled after adjusting the composition.

[0015] In a third aspect, the present invention provides the use of any one of the electrolytes described in the deep discharge of waste lithium-ion batteries.

[0016] In a fourth aspect, the present invention provides application of the method in recycling waste lithium-ion batteries.

[0017] The principle of the electrolyte design of the present invention is to ensure that only metal deposition and oxygen precipitation occur during the electrolysis process. Since the waste lithium-ion battery has residual voltage, it can trigger an electrolysis reaction when immersed in the above electrolyte. During the positive electrode reaction, the oxygen precipitation reaction should occur first, so as to ensure that the reaction process has no risk of explosion and is environmentally friendly. During the negative electrode reaction, metal ions should be preferentially released over hydrogen ions (H + / H3O + , acidic solution) or water molecules (alkaline solution) discharge, and then metal electrodeposition occurs to avoid the generation of hydrogen. To this end, in addition to metal ions such as copper, mercury, silver, platinum, and gold whose deposition potential is higher than the hydrogen evolution potential, solutions containing other metal ions need to form complexes or adjust the pH value to make the metal deposition potential higher than the hydrogen evolution potential.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) During the chemical discharge process of waste lithium-ion batteries, no hydrogen is produced, there is no risk of combustion or explosion, it is green and safe, and there is no need to operate in open spaces, achieving safe and green deep discharge.

[0020] (2) The electrolyte can be reused, and the battery shell undergoes a metal deposition process with little corrosion. After the battery shell is recycled, the metal deposited on the battery shell can be recycled and reused through appropriate acid treatment, thereby reducing operating costs.

[0021] (3) The present invention has a simple operation process. It adopts a chemical discharge method to directly immerse the waste lithium-ion battery in a prepared electrolyte, and uses the residual voltage of the battery to trigger a chemical reaction to control the battery discharge time. When the battery is completely discharged, it is removed from the solution, cleaned, and then enters the next step.

[0022] (4) The electrolyte of the present invention has a simple and inexpensive composition, low raw material cost, and is easy to apply in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the process of chemically discharging waste lithium-ion batteries using the chemical method of the present invention;

[0024] Figure 2 This is a voltage-time relationship diagram of a waste lithium-ion battery in a copper sulfate solution;

[0025] Figure 3 Analysis of gas composition generated by discharging waste lithium-ion batteries in copper sulfate solution;

[0026] Figure 4 It is the voltage-time relationship diagram of the waste lithium-ion battery in the sodium chloride solution;

[0027] Figure 5 Analysis of hydrogen and oxygen generated by discharging spent lithium-ion batteries in sodium chloride solution;

[0028] Figure 6 It is the voltage-time relationship diagram of the spent lithium-ion battery in the alkaline zinc sulfate solution;

[0029] Figure 7 Analysis of gas composition generated by discharge of spent lithium-ion batteries in zinc sulfate solution. DETAILED DESCRIPTION

[0030] The present invention will be further described below by means of drawings and embodiments.

[0031] Embodiment 1:

[0032] Copper sulfate solution is selected as the electrolyte for chemical discharge of waste lithium-ion batteries. In the copper sulfate solution, oxygen is mainly formed at the positive electrode, and copper ions on the negative electrode are preferentially reduced to metallic copper on the battery shell over hydrogen ions. Therefore, the discharge process only produces oxygen, no other waste gas, and no risk of explosion. Therefore, it is green and safe, and does not need to be operated in an open space. The specific implementation methods include:

[0033] (1) Discharge methods and requirements for waste lithium-ion batteries

[0034] The chemical discharge method is used to immerse the waste lithium-ion battery directly in the prepared electrolyte, and the residual voltage of the battery is used to trigger a chemical reaction. The battery discharge time is controlled until the voltage is below 1V to complete the discharge process. When the battery is discharged, it is removed from the solution, cleaned and then enters the next step. Schematic diagram of the chemical discharge process of waste lithium-ion batteries by chemical method.

[0035] (2) Chemical discharge of spent lithium-ion batteries in copper sulfate solution

[0036] Used lithium-ion batteries were placed in 0.5, 0.75 and 1 mol L -1 The discharge phenomenon was observed and the battery voltage change was detected at any time in a copper sulfate solution of 0.5, 0.75 and 1 mol L -1 The time required to discharge to 1V in the copper sulfate solution is 590min, 680min and 810min respectively. At this time, the pH value of the solution rises to about 4. Figure 2 As shown in Figure 2. During the deep discharge process, the hydrogen and oxygen components produced were analyzed by in-situ gas phase mass spectrometry. Figure 3As shown, the output of oxygen gradually increases with the discharge, and the output tends to be stable at 950s, and no hydrogen is produced throughout the process.

[0037] Comparative Example 1:

[0038] Used lithium-ion batteries were placed in 0.5, 0.75 and 1 mol L -1 The discharge phenomenon was observed and the battery voltage change was detected at any time in a sodium chloride solution of 0.5, 0.75 and 1 mol L -1 The time required for the sodium chloride solution to discharge to 1V is 275min, 300min and 330min respectively. At the end, the pH value of the solution rises to about 8. Figure 4 As shown in Figure 2. During the deep discharge process, the hydrogen and oxygen components produced were analyzed by in-situ gas phase mass spectrometry. Figure 5 As shown, as the discharge process proceeds, almost no oxygen is produced, but a large amount of hydrogen is produced.

[0039] Embodiment 2:

[0040] Zinc sulfate solution is selected as the electrolyte, and the solution is adjusted to alkaline for chemical discharge of waste lithium-ion batteries. In the alkaline zinc sulfate solution, oxygen is mainly formed at the positive electrode, and the hydroxy zinc complex ions on the negative electrode are reduced to metallic zinc before hydrogen ions. Therefore, the discharge process only produces oxygen, no other waste gas, and no risk of explosion. Therefore, it is green and safe, and does not need to be operated in an open space.

[0041] (1) Discharge methods and requirements for waste lithium-ion batteries

[0042] The chemical discharge method is used to immerse the waste lithium-ion battery directly in the prepared electrolyte, and the residual voltage of the battery is used to trigger a chemical reaction. The battery discharge time is controlled until the voltage is below 1V to complete the discharge process. When the battery is discharged, it is removed from the solution, cleaned, and then enters the next step.

[0043] (2) Chemical discharge of spent lithium-ion batteries in zinc sulfate solution

[0044] Used lithium-ion batteries were placed in 0.5, 0.75 and 1 mol L -1 The discharge phenomenon was observed and the battery voltage change was detected at any time in a zinc sulfate solution. The zinc sulfate solution was adjusted to a pH of about 9. After the battery was placed in the solution, only the positive electrode had obvious bubbles, and the negative electrode gradually had gray-white metallic zinc deposits. -1In the zinc sulfate solution, the time required to discharge to 1V is 780min, 800min and 940min respectively, and the pH value of the solution rises to about 11 at the end. Figure 6 As shown in Figure 2. During the deep discharge process, the components of hydrogen and oxygen produced are analyzed by in-situ gas phase mass spectrometry. Figure 7 As shown, the output of oxygen gradually increases with the discharge, and the output tends to be stable after 1000s, and no hydrogen is produced throughout the process.

Claims

1. An electrolyte for deep discharge of waste lithium-ion batteries, characterized in that: The anions in the electrolyte are one or a combination of hydroxide ions, sulfate ions, carbonate ions, nitrate ions, phosphate ions or perchlorate ions; The cations in the electrolyte are one or a combination of metal ions or metal complex ions that can be electrodeposited in an aqueous solution.

2. An electrolyte for deep discharge of waste lithium-ion batteries as claimed in claim 1, characterized in that: The metal ions that can be electrodeposited in the aqueous solution are one or a combination of chromium ions, manganese ions, iron ions, cobalt ions, nickel ions, copper ions, zinc ions, gallium ions, tellurium ions, ruthenium ions, rhodium ions, palladium ions, silver ions, cadmium ions, indium ions, tin ions, antimony ions, rhenium ions, osmium ions, iridium ions, platinum ions, gold ions, mercury ions, thallium ions, lead ions, bismuth ions or polonium ions.

3. A method for deep discharging of waste lithium-ion batteries, characterized in that: The following steps are involved: The waste lithium-ion battery is immersed in the electrolyte as claimed in claim 1 or 2, wherein the deposition potential of the metal ions in the electrolyte is higher than the hydrogen evolution potential, and a discharge chemical reaction is performed to a voltage of 1V or less to complete the deep discharge of the waste lithium-ion battery, and the electrolyte and the battery are collected separately.

4. The method according to claim 3, characterized in that When the deposition potential of the metal ions in the electrolyte is not higher than the hydrogen evolution potential, a metal ion complex is formed to make the hydrogen evolution potential lower than the metal deposition potential.

5. The method according to claim 3, characterized in that The metal ion complex is formed by adjusting the pH value or adding a ligand.

6. The method according to claim 3, characterized in that The collected electrolyte can be recycled after adjusting the composition.

7. Use of the electrolyte as claimed in claim 1 or 2 in deep discharge of waste lithium-ion batteries.

8. Use of the method according to any one of claims 3 to 6 in the recycling of waste lithium-ion batteries.

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